This invention relates to the construction and attachment of partial artificial dentures, and particularly to the structure of such attachments and the process of manufacturing them.
The most common form of partial artificial denture, sometimes referred to as partial plate, involves the use of wire-like clasps or the like which engage around one or more of the wearers remaining teeth, and which hold the denture in position. Considerable difficulty is experienced with such arrangements breaking, bending and losing their holding force, or otherwise changing the predetermined position of the partial denture to the point where it is uncomfortable and possibly irritates the wearer, and/or is subjected to unusual stresses which results in breakage, either of the attachment parts or in some cases the partial denture itself. Furthermore, existing attachment arrangements are somewhat limited in their application, and particularly have not been found suitable for partial dentures which might be required on only one side of the patient's mouth.
Furthermore, existing retention arrangements involve silver solder or similar connections which tend to break, and which are particularly sensitive to flexing which may occur during usage of the denture, yet it is desirable that the attachment of the denture to the existing teeth be somewhat flexible, so that stresses are not transferred to the anchoring existing teeth, thereby compounding the dental problem of the wearer.
Various attachment devices of this nature are disclosed in U.S. Pat. Nos. 1,299,364; 1,367,885; 1,423,288; 1,696,422; 1,805,264; 3,309,771; 3,535,787; and 3,990,150. Of these, the most significant is U.S. Pat. No. 1,299,364 which shows a partial dental bridge having wire or hard metal anchors embedded therein, and extending in the form of a vertically oriented loop with both of its ends fixed to the bridge. An abutment is attached to a natural tooth, and a keeper in the form of a hard metal plate is soldered to the abutment.
The keeper is formed with grooves in its side and top, to receive the anchor loop, which is arranged to snap around the generally rectangular extent (in cross-section) of the groove. Thus any pivoting of the bridge along an axis transverse to the attachment must overcome the stiffness of the hard wire at the base ends of the loop; and any rotational motion of the loop around the groove must overcome (and tend to weaken) the clasping action of the wire loop against the sides of the groove in the keeper. Thus, stresses due to flexing lengthwise of the jaw tend to misalign the attachment loop and bend or work the wire, while torque tending to rotate the loop will tend to transmit into the keeper.